Doctor of Philosophy (PhD)
The use of point-of-care (POC) diagnostic systems holds great promise for the early detection of various diseases. However, detection limits for commercially available POC systems have not been able to meet the lower cutoffs offered by the specialized laboratory testing methods. Research into the use of carbon nanofibers (CNFs) grown on glass microballoons in POC devices was studied. The growth of several millions of the CNFs on each microballoon (NMBs) presented a large surface area with high probability of capturing minute concentrations of biospecies. Functionalization of the NMBs with the carboxyl group needed for biospecies conjugation was achieved by air oxidation. This oxidation process makes our process environmental friendly to other downstream processes. Primary IgG was immobilized on glass slides. An immunochromatographic device was developed using a sandwich assay protocol to detect varying concentrations of immobilized anti-IgG on the slides. Covalent conjugated NMBs with secondary IgG were used in generating both visual and electrical signals. False signals were prevented by coating both the antibody immobilized slides and NMBs with surfactants. A lower visual detection limit of 0.010 ng/ml and faster detection (~ 1 min) were achieved for the IgG/anti-IgG detection. This promising result led to the modification of the immunochromatographic device for the detection of malaria infection and pregnancy. Plasmodium falciparum histidine rich protein-2 (PfHRP-2) and Plasmodium vivax merozoites surface protein-1 (PvMSP-1) antigen were used for malaria testing. Human chorionic gonadotropin (hCG) was also used for pregnancy testing. The approach made it possible to detect PfHRP-2 and PvMSP-1 in PBS over their linear range of 0.01 – 10 ng/ml. The ultrasensitive approach resulted in detecting as low as 0.025 ng/ml of PfHRP-2 and 0.025 ng/ml of PvMSP-1in PBS using visual signal within only one minute of testing. The approach is highly selective and specific in identifying PfHRP-2 from a mixed solution of PfHRP-2 and PvMSP-1. A visual detection limit of 0.050 ng/ml of hCG in PBS was also obtained for the pregnancy antigen. Thus, the highly reactive, rapid, selective and signal amplification capabilities of NMBs is a promising tool for use in POCs for the early diagnosis of malaria and pregnancy.
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Gikunoo, Emmanuel, "Utilization of Carbon Nanofibers Grown on Glass Microballoons (NMBs) in Point-of-Care Diagnostic Devices" (2014). LSU Doctoral Dissertations. 2010.